Stacked spiral resonator



1931- v M. R. HUTCHISON, JR 1,336,075

STACKED SPIRAL RESONATOR Filed Aug. 6. 1927 2 Sheets-Sheet 1 vINVEINTOI'Q. 071719! R993 ef/uzalmamllr ATTORNEY.

1931. M. R. HUTCHISON, JR ,075

STACKED SPIRAL RESONATOR Filed Aug. 6. 1927 2 Shegts-Sheet 2 I N VENTOR. Willa/- ReeseM/fafi/M/I BYQM ' ATTORNEY.-

Patented Dec. 15, 1931 UNITED STATES PATENT OFFICE MILLER, REESEHUTCEISON, JR, OF MADISON, NEW JERSEY, ASSIGNOR, BY MESNE 5S- SIGNMENTS,TO SONORA MANUFACTURING CORPORATION, A CORPORATION OF ILLINOIS STACKEDSPIRAL RESONATOR Application filed August 6, 1927. Serial No. 211,020.

This invention relates to sound propagating devices and, moreparticularly, to apparatus for translating electromagnetic impulses intosound vibrations.

In electromagnetic sound propagating devices vibrations are set up in amechanical diaphragm which fluctuates in position in accordance with anapplied electric current. The diaphragm is displaced in space to producevibrations of an amplitude proportional to the instantaneous value ofthe applied electric current and, in so vibrating, operates on theadjacent fluid medium to produce compressions and rarefaction thereinwhich travel as sound waves and produce corresponding vibrations in thehuman ear drum.

In orderto assist the propagation of the above mentioned sound waves ina fluid medium, it is desirable to provide resonating devices such ashorns, which are ca able of receiving waves produced by the vi ratingdiaphragm and amplifying the same before impressing them upon thesurrounding atmosphere. Horns of the usual type amplify most stronglywaves of a definite frequency to which they are resonant. For example,an open end organ pipe will amplif most readily a wave of twice its ownlengt In addition to its fundamental note,various overtones andharmonics thereof are amplified by a resonating device. However, notesof a requency lower than the fundamental are largel suppressed. In orderto accurately repro uce notes throughout the musical range it istherefore necessary to design the resonating chamber to transmit thelowest desired fundamental since the attenuation of the higher notes ofsuch a horn is less than the attenuation of notes below the fundamentalfrequency.

In order to reproduce the various notes of the chromatic scale, it hasbeen found desirable to provide a plurality of horns, each of which isresonant at a different frequency in said scale. When sound wavesrepresenting music are impressed on a bank of such horns, each willamplify most strongly notes of its own fundamental frequency andharmonies thereof. Consequently each musical note will be selected andamplified by a different individual horn. Since the notes of thechromatic scale are twelve in number, it has been found desirable toemploy a series of twelve horns, ea ch tuned to a different note of oneof the lower octaves of a chromatic scale.

This invention provides a series of sound-' ing chambers which areranged in compact form and occupy a minimum amount of space. Thechambers are especially designed to propagate efficiently sound wavesofthe vari-- ous frequencies and to impress such waves upon thesurrounding fluid medium such as air. In accordance with this invention,a plurallty of spiral chambers are provided through which the soundwaves of various frequencies are selectively amplified and propagated.The spiral chambers may be arranged in parallel planes with theiropenings facing in the same direction whereby the desirable directionalcharacteristics usually required of horns and other sound propagatingdevices may be obtained.

The invention also consists in certain new and original features ofconstruction and combinations of parts hereinafter set forth andclaimed. Although the novel features which are believed to becharacteristic of this invention will be particularly pointed out in theclaims appended hereto, the invention itself, as to its objects andadvantages, the mode of its operation and the manner of its organizationmay be better understood by referring to the following description takenin connection with the accompanying drawings forming a part thereof, inwhich Fig. 1 is a perspective view of a sound propagating deviceconstructed in accordance with this invention;

Fig. 2 is an: elevation thereof Fig. 3 is a section taken on the line 33of Fig. 2 showingdetails of the clani'pingmeans;

Fig. 4 is a side elevation of a plate and spiral spacing ribbon forminga chamber, resonant at a definite-frequency;

Fig. 5' is an end elevation thereof;

Fig. 6 isa side elevation of a plate and spac- Like reference charactersdenote like parts in the several figures of the drawings;

In the following description and in the claims parts will be identifiedby specific names for convenience, but they are intended to be asgeneric in their application to similar parts as the art will permit.

Referring to the drawings more in detail, in which a particularembodiment of the invention is disclosed for purposes of illustration,the reproducing device is shown as comprising a plurality of plates 10having an irregular contour, aportion 11 of which may be in the form ofa spiral. PlateslO are provided with an opening 12 through which thesound waves produced by the electromagnetic means, which will behereinafter described, may pass. Spiral spacing members 1% are locatedbetween adjacent plates 10 and in conjunction therewith form spiralsounding chambers of constantly increasing cross section] Spacingmembers l l may be formed of any desired material such as a flat ribbonwhich has been bent in the spiral form. Metallic ribbons have been foundpreferable although other materials may be used if desired.

Logarithmic spirals have been formed to possess the characteristicsdesired in sound propagating devices and to be particularly adapted tothe transmission of soundwaves. Spirals of other-forms may be used,however, for the transmission of sound waves 1 however, platesplates,suitable clamping and may approximate the results obtained by thelogarithmic spiral. v

vRibbon 14 may be attached to plates by any desirable means as forexample by grooves I 15 (Fig. 7 which may be cut in the face of saidplates, said ribbons being pressed into and rigidly held by saidgrooves. If desired, 10 may be covered with a coating of an adhesivematerial such as shellac and ribbons ll pressed in firm engagement withthe face of said plates and held in such position by the adhesiveproperties of the material. i

A plurality of plates 10 and ribbons 14 may be placed in stackedformation as shown in Fig. 2 and firmly secured together as by rods 16passing through aligned holes in said bushings 17 being provided forproperly spacing and clamping the va rious elements. The assembly may befurther clamped by means of rod 18passing through aligned holes 12 andco-operating with disc 19 and open tubular member .ber 20 to be firmlyheld in position against the face of )late 10.

l V An electromagnetic unit 23 of any desired type, having a vibrat ngdiaphragm operated by electromagnetic means maybe supported by member 20and so positioned that the vibrating diaphragm may produce compressionsand rarefactions in the air column formed withinallgned openings 12 ofplates 10. The particular form of re 3IOdUC1II l b unit, however, formsno part of the present an electromagnetic reproducinvention andconsequently will not be described herein in detailr The various spiralhambers formed between saidplates 10 may be designed to be resonant towaves orvarious frequencies by suitably controlling the convolutions ofspiral ribbons 14. V In the interest of the outside appearance of thecompleted assembly, the outer portion of said ribbons 1% should belocated at corresponding places on the various plates 1G as for exampleof the upper corner thereof. The length of the ribbon, however, and thelength of ti e air column enclosed thereby may be varied by terminatingthe inner end of said ribbon at various points around the periphery ofopening 12. Figs. l and 6 show, by wayrof example, ribbons in whichdifferent total lengths are obtained by varying the rate ofcurvature andthe angular position of the inner end thereof.

The outer opening of the air columns may beformed of the same size bythe addition of spacin member 30 (Fig. 8) formed as a continuation of aportion of spiral ribbon 14 and extending between said ribbon and thefront portion ofplates 10. Said member 30, in conjunction with the outerportion of spiral ribbon 1 L, forms a flare through which the soundwaves from thespiral chambers willbe impressedon the surrounding medium.Cover member 31 9) may be located around the various plates 10 betweenthe outer end of ribbon 14 and the corresponding end of member 30 inorder to produce a neat and pleasing finished appearance. i

The fundamental note wh ch maybe prop agated by a given air chamber isdetermined. by therate of increase in cross section of said chamber aswell as by the total length thereof. Spiral members 14. shouldpreferably be so designed that the air chambers will be of the properlength and of the required cross sections to produce high quality ofreproduction. A plurality of such devices, con structed in accordancewith the present invention, each of which is differently charac terized,will serve to selectively amplify and reproduce the various.musicalnotes which may be impressed thereon and to propagate such notesto the surrounding medium. Sound waves comprising compressions andrarefactions produced by the diaphragm of the electromagnetic unit willbe propagated through the various alinged openings 12 in plates 10 andwill act upon the various spiral resonating chambers opening thereon.

Since the outer portions of spacing members 14 are located in alignedposition, the various air columns will open in the same direction andsimultaneously propagate the waves upon the surrounding medium in thatdirection.

This invention has been described as comprising a bank of 12 chambers.However, other numbers of chambers may be employed if desired and theabove-mentioned condi tions approximated thereby. For example, sevenchambers may be so selected as to propagate substantially equally thevarious musical notes. It has been found that in order to properlytransmit notes at the lower end of the musical scale, the rate ofincrease in area of the resonating chambers per unit of length should below. The spiral chamber should therefore be formed with a plurality ofconvolutions of slowly increasing cross sections and member 30 designedto cooperate with the outer portion of spacing member 14 to obtain thesame increment in cross section.

The device constructed in accordance with the present invention iscompact and occupies a minimum amount of space consistent with theaccurate reproduction of the various musical notes. The assembly isentirely self-contained and by reason of its rigid construction may bemoved from place to place without danger of injury. Furthermore, a neatappearance is produced since the various resonating columns arecontained in a single unitary structure. It has been found that alogarithmic spiral is particularly adapted for the eflicient propagationof sound waves although various modifications may be employed withoutappreciably affecting the quality of the reproduced notes.

In the drawings accompanying and forming part of this specification, apractical commercial embodiment of the invention is shown, but as suchillustration is rimarily for purposes of disclosure, it will beunderstood that the structure may be modified in various respectswithout departure from the broad spirit and scope of the invention ashereinafter defined and claimed.

l/Vhat is claimed is:

1. A sound propagating device comprising a plurality of spaced platesarranged in stack formation, fiat spiral spacing members therebetween,said plates having aligned openings at the innermost ends of saidspacing members whereby sound waves may be propagated therethrough andimpressed upon the spiral chambers produced by each of said members.

2. A sound propagating device comprising a plurality of spiral chambersformed by flat plates and spiral spacing means therefor, said chambershaving aligned openings, aligned openings in said plates at theinnermost ends of said chambers and means for impressing sound wavesthereon.

3. A spiral resonating chamber comprising a pair of flat plates and afiat spiral member therebetween and a spacing member forming with theouter portion of said spiral member aflared opening.

4. A sound propagating device comprising a plurality of flat platesarranged in spaced and parallel relationship, flat spiral spacingmembers therefor, clamping means comprising rods extending through saidassembly, a reproducing unit and an open tubular support therefor, a rodextending through aligned openings in said plates for clamping saidsupport thereto, each of said spiral members forming in connection withthe adjacent plates a spiral air column resonant to a different note inthe chromatic scale.

5. In combination with a sound reproducing device, a plurality ofresonating chambers in the form of logarithmic spirals, each of saidchambers being resonant to a different note in the chromatic scale.

6. A sound propagating device comprising a plurality oflogarithmetically determined spiral sound propagating chambers, eachtuned to a separate note of the chromatic scale, and a single vibrationimparting unit for all of said chambers.

7. A sound propagating device comprising a plurality of fiat sidedspiral wall sound propagating chambers, each of said chambers beingtuned to a separate note of the chromatic scale, and a single vibrationimparting unit for all of said chambers.

Signed at New York, in the county of New York and State of New York,this 5 day of August A. D. 1927.

MILLER REESE HUTCHISON, JR.

